Recently released FBI files about the Occupy movement do not reveal the kind of dirty tricks J. Edgar Hoover's bureau used against demonstrators in the Bay Area during the '60s, but they present some striking parallels to those dark days and have rightly raised concern among civil libertarians.

Though fragmentary, the records provide a window on the FBI's monitoring of protest and show that over the decades the machinery of surveillance remains much the same, even as expanded intelligence powers and technological advances magnify potential abuse.

As in the '60s, the FBI reports use sweeping language like "potential terrorist threat" to characterize nonviolent dissent. As then, the bureau exchanges information with a vast network of federal agencies, state and local police, campus cops and corporate security. And once again the FBI is invoking great secrecy. Such activity, Congress found in the '70s, contributed to massive intelligence abuses.

The FBI released 99 heavily redacted pages and withheld 288 more in response to a Freedom of Information Act request from the Partnership for Civil Justice Fund, a public-interest legal organization in Washington, D.C. The records show the complexity and contingencies in government preparation for demonstrations that could disrupt businesses and public places. They reflect official concern about violent individuals possibly joining protests unbeknown to protest planners, as well as opponents' threats against Occupy.

Even while noting Occupy organizers do "not condone the use of violence," the records show that FBI field offices across the nation collected information on the premise the protests posed a potential "terrorist" or "criminal" threat. Some samples:

-- FBI agents gathered intelligence on Occupy's plans before September 2011, when Occupy Wall Street made camp at Zuccotti Park in Manhattan, igniting a national movement against income disparity.

-- The Jacksonville, Fla., office held a "domestic terrorism" briefing that October on "the spread of the Occupy Wall Street Movement." An FBI official suggested contacting Occupy organizers in case the organizers noticed "violent tendencies by attendees." The official also reported "a long-term plot to kill local Occupy leaders via sniper fire."

-- An FBI bulletin meanwhile warned corporate security officers that Occupy planned to shut West Coast ports. The bulletin's stated purpose was to "raise awareness of this type of criminal activity," though it noted protesters planned no violence. But they say nothing about the FBI's reported infiltration of Occupy.

The bureau shared information on Occupy with police on joint terrorism task forces, which have raised concerns about skirting local surveillance restrictions, and with fusion centers, regional intelligence hubs recently criticized by Congress as violating civil liberties. The FBI's Domestic Investigations and Operations Guide prohibits investigations based solely on First Amendment activity, but permits "assessments" even when there is "no particular factual predication" of potential crimes or national security threats. Although they are relatively circumscribed, assessments may continue "as long as necessary" and draw on public information, government records, online resources, confidential sources and physical surveillance.

Several of the FBI reports on Occupy noted their contents were unconfirmed and a "presumption of innocence still exists."

And none of them (as produced) reveal unlawful activities like the FBI's investigation and harassment at the University of California in the '60s. As FBI files released to me pursuant to several lawsuits under the Freedom of Information Act show, and as the courts in those cases concluded, the bureau went far beyond legitimate investigation of the 1964 Free Speech Movement at UC Berkeley and sought to "disrupt" and "neutralize" it under Hoover's Cointelpro operation.

FBI agents collected tax returns, phone data and medical information on Free Speech Movement leader Mario Savio and targeted him for disruption because they deemed him "subversive," a term with no legal definition. Bureau officials abused their power in an effort to get UC President Clark Kerr fired because they disagreed with his politics and handling of campus matters. The FBI secretly gave Gov. Ronald Reagan (an FBI informer in his Hollywood days) intelligence reports he could use to crack down on campus dissent.

The FBI today is far more accountable, and Director Robert Mueller III is no Hoover. But as U.S. Sen. Frank Church's committee found during its groundbreaking hearings, the FBI's use of "broad and imprecise labels" and wide dissemination of such allegations led to dossiers on hundreds of thousands of law-abiding citizens, the use of intrusive investigative methods like warrantless searches, and many damaged lives.

"In time of crisis, the Government will exercise its power to conduct domestic intelligence activities to the fullest extent," the committee warned in 1976. "The distinction between legal dissent and criminal conduct is easily forgotten."

Seth Rosenfeld is the author of "Subversives: The FBI's War on Student Radicals, and Reagan's Rise to Power" (Farrar, Straus and Giroux).